JPH1191318A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve brake performance without increasing rolling resistance. SOLUTION: In this tire, by recessing side wall faces 18A, 18B along the tire circumferential direction of a block 18 in the circular arc shape, rubber volume near the side wall faces 18A, 18B is reduced, and therefore, neighbors of the side wall faces 18A, 18B easily expand circumferentially and radially of the tire even when rubber whose dynamic modulus of elasticity E' is high to improve performance of the first half of the brake. Therefore, even when tire circumferential side wall face neighbors separate from a road surface 22 for prior blocks due to slow return of the neighbors of the side wall faces, in this block 18, the neighbor of an end 20D of a tread 20 is still grounded, actual grounding area is larger than that for the prior block, and performance on the second half of the brake is improved. Because brake performance can be improved without changing area (negative radio) of the tread 20, rolling resistance does not increase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire having a block putter, and more particularly to a pneumatic tire having improved braking performance.

[0002]

2. Description of the Related Art In a pneumatic tire having a block pattern, a friction coefficient (μ) with a road surface has been conventionally improved to improve braking performance.

[0003] It is known that the friction coefficient μ is related to the grip of a tire, and the larger the better, the better the braking performance.

[0004]

However, when the coefficient of friction with the road surface is increased, there is a problem that the rolling resistance increases and the fuel consumption characteristics deteriorate.

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire that can improve braking performance without increasing rolling resistance.

[0006]

As a result of repeated experiments and studies by the inventor, as a physical property of rubber, in addition to the friction coefficient μ, the dynamic elastic modulus E ′ and the tensile stress M ₃₀₀ at the time of elongation at 300% have an influence on the braking performance. It turned out that the impact was great.

The dynamic elastic modulus E 'is related to the block rigidity at the beginning of braking, and it has been found that the larger the dynamic elastic modulus E', the better the performance at the beginning of braking.

The tensile stress M ₃₀₀ at 300% elongation is related to the block rigidity in the latter half of the brake. To improve the performance in the latter half of the brake, the tensile stress M 300 at 300% elongation is improved.
It turned out that the smaller the _{300, the} better.

The reason will be described below. First, the initial stage of the brake will be described.

In the early stage of the brake, it is important to secure the contact area by preventing the block from falling down at the time of contact with the ground. By increasing the dynamic elastic modulus E 'and securing the block rigidity, the performance in the early stage of the brake is improved. Can be improved.

Next, the latter half of braking will be described. When the pneumatic tire rotates on the road surface, the rubber block comes into contact with the road surface and is compressed in the radial direction of the tire.

On the other hand, in a pneumatic tire, in order to improve braking performance, it is necessary to increase a real ground contact area (an area where a block is actually in contact with a road surface).

For example, a tensile stress M ₃₀₀ at 300% elongation
From the prepared respective tires small rubber block and large rubber block, when the rolling, the tensile stress M ₃₀₀ is small rubber block compressive deformation after the road surface than the blocks of greater stress M ₃₀₀ tensile rubber towards Until they leave, the block tends to stretch greatly to the kick-out side.

Therefore, considering a block of a rotating tire moving away from the road surface, a block having a large rubber tensile stress _M300 is easy to separate from the road surface due to a small amount of elongation of the block. in M ₃₀₀ is small block block end still in the ground state (since the time in contact with the ground for growth of the block end is large is increased.).

[0015] As a result, the actual ground contact area towards the rubber tensile stress M ₃₀₀ is more the smaller the tensile stress M ₃₀₀ of the rubber than the block of large blocks is increased, thereby improving the brake performance.

However, the dynamic elastic modulus E 'is increased at the end.
The tensile stress M at 300% elongation ₃₀₀Induce an increase in
The brakes even if the performance of the first half of the brakes is improved.
The performance in the latter half has deteriorated, and as a result
The performance of the rubber does not improve, that is, changing the properties of the rubber
Then it is difficult to balance the performance of the first half of the brake and the performance of the second half
there were.

As a result of intensive studies by the inventor, even when the dynamic elastic modulus E 'of the block rubber is increased, the tensile stress M at 300% elongation can be obtained by optimizing the block shape.
It was found that the same effect as when ₃₀₀ was reduced was obtained.

The invention according to claim 1 has been made in view of the above fact, and is a pneumatic tire having a block pattern on a tread, wherein a side of a side wall surface of the block along a tire circumferential direction. At least one of the wall surfaces is characterized in that it is recessed inward of the block from a straight line in the tire radial direction set at the end of the block.

The side surface along the tire circumferential direction includes not only the side wall surface which coincides with the tire circumferential direction, but also includes a side wall surface which tends toward the tire circumferential direction at a predetermined angle. There is no intention.

Next, the operation of the pneumatic tire according to the first aspect will be described. By denting the side wall surface along the tire circumferential direction of the block, the rubber volume near the side wall surface is reduced. As a result, even if a rubber having a high dynamic elastic modulus E ′ is used to enhance the performance in the first half of the brake, The vicinity of the side wall surface is easily extended in the tire circumferential direction and the radial direction.

Therefore, when the compressed block is going to be separated from the road surface, the recessed side wall surface portion is easily extended, the time for which the end of the side surface portion is in contact with the ground becomes longer, and the block of the block which is going to be separated from the road surface is increased. The decrease in the actual contact area can be suppressed, and the performance in the latter half of the brake can be improved as compared with the related art.

Further, in the pneumatic tire according to the first aspect, since the coefficient of friction with the road surface is not increased by changing the area of the tread of the block or the like, it is possible to reduce other performances such as an increase in rolling resistance. Absent.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the side wall surface is a reverse tapered surface whose base side is inclined inwardly of the block with respect to the tread surface side of the block. Features.

[0024] In the pneumatic tire according to the second aspect, the side wall surface of the block in the tire circumferential direction is a reverse tapered surface in which the base side is inclined inward from the tread portion side toward the inside of the block, so that the vicinity of the side wall surface is provided. Rubber volume decreases, and it becomes easy to extend in the tire circumferential direction and the tire radial direction.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, the inclination angle of the side wall surface with respect to the tire radial direction is set at 5 to 35 degrees.

When the inclination angle of the side wall surface with respect to the tire radial direction is less than 5 degrees, the rubber volume near the side wall surface does not decrease so much, and it becomes difficult to extend in the tire circumferential direction and the tire radial direction.

On the other hand, when the angle of inclination exceeds 35 degrees, the block easily falls down. Therefore, in order to surely obtain the effect of the present invention without deteriorating other performances, the inclination angle should be 5 to 3 degrees.
It must be set to 5 degrees.

According to a fourth aspect of the present invention, in the pneumatic tire according to the first aspect, the side wall surface is an arcuate curved surface.

[0029] In the pneumatic tire according to the fourth aspect, the side wall surface in the tire circumferential direction of the block is formed into an arcuate surface, so that the rubber volume near the side wall surface is reduced, so that the block in the tire circumferential direction and the tire radial direction is reduced. Easy to stretch.

According to a fifth aspect of the present invention, in the pneumatic tire according to the fourth aspect, the radius of curvature of the arcuate curved surface is 2/3 to 3 times the block height.

When the radius of curvature of the arcuate curved surface exceeds three times the block height, the rubber volume near the side wall surface does not decrease so much and it becomes difficult to extend in the tire circumferential direction and the tire radial direction.

On the other hand, if the radius of curvature of the arcuate curved surface is less than 2/3 of the block height, the block tends to fall down.

Therefore, in order to surely obtain the effect of the present invention without deteriorating other performances, it is necessary to set the radius of curvature of the arcuate curved surface to 2/3 to 3 times the block height.

According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects,
The rubber constituting the block has a dynamic elastic modulus E ′ of 0.
60 × 10 ⁸ dyn / cm ² <E ′ <1.50 × 10 ⁸ dyn / cm ² , and the tensile stress M ₃₀₀ at 300% elongation is 60 kgf / cm ² <
M ₃₀₀ <150 kgf / cm ² .

In the initial stage of braking, the deformation of the block is small, and the larger the dynamic elastic modulus E ', the more effective the bulging.

[0036] the second half of the brake, in order to block the deformation area is the very type, not out initial of such hold out effect, is enough large but rather 300% growth ease of extension tensile stress M _300, easy to capture the road surface ( μ up).

Here, the dynamic elastic modulus E ′ is 0.60 × 10
^{If it is} less than ⁸ dyn / cm ² , the initial braking level will be reduced. On the other hand, the dynamic elastic modulus E ′ is 1.50 × 10 ⁸ dyn
If it is larger than / cm ² , other performance (ride comfort) will be reduced.

The tensile stress M ₃₀₀ at 300% elongation is 6
If it is less than 0 kgf / cm ² , the blocks move too much and the performance is reduced. On the other hand, the tensile stress M ₃₀₀ at 300% elongation is 15
If it is larger than 0 kgf / cm ² , the effect of elongation cannot be obtained.

Therefore, in order to surely obtain the effect of the present invention without deteriorating other performances, the dynamic elastic modulus E ′ of the rubber constituting the block is set to 0.60 × 10 ⁸ dyn / cm ² <E ′ <1. .50
× 10 ⁸ dyn / cm ² , tensile stress at 300% elongation M ₃₀₀ of 60
It is preferable that kgf / cm ² <M ₃₀₀ <150 kgf / cm ² .

It should be noted that 1.00 × 10⁸dyn / cm^Two<E '<
1.35 × 10⁸dyn / cm^Two, 85kgf / cm ^Two <M₃₀₀<12
5kgf / cm^Two More preferably,

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIGS. 1A and 1B, the tread 12 of the pneumatic tire 10 of the present embodiment has a plurality of blocks 1 by a plurality of circumferential main grooves 14 and a plurality of lateral grooves 16.
8 are sectioned.

Two rows of blocks 1 on both sides of the tire equatorial plane CL
8 is a straight line in the tire radial direction in which the side wall surfaces 18A and 18B of the block 18 along the tire circumferential direction pass through the tire circumferential end portions 20A and 20B of the new tread surface 20 of the block 18 as shown in FIG. It is depressed in an arc shape inside the block from S.

The negative ratio of the tread 12 is preferably 20 to 35% as in the past. It is preferable that the radius of curvature R of the arcuate curved surfaces of the side wall surfaces 18A and 18B be set to 2/3 to 3 times the block height H.

The outermost block 18 in the tire width direction
Is that the side wall surface of the circumferential main groove 14 has the above-described side wall surface 18A,
As in 18B, it is recessed in an arc shape inside the block.

The rubber constituting the block 18 has a dynamic elastic modulus E ′ of 0.60 × 10 ⁸ dyn / cm ² <E ′ <1.5.
0 × 10 ⁸ dyn / cm ² , 300% elongation tensile stress M ₃₀₀ is 6
It is preferable that 0 kgf / cm ² <M ₃₀₀ <150 kgf / cm ² .

Next, the operation of the present embodiment will be described. The side wall surfaces 18A, 18B of the block 18 in the tire circumferential direction are recessed in an arc shape to form the side wall surfaces 18A, 18B.
The rubber volume in the vicinity of B decreases, and as a result, even if rubber having a high dynamic elastic modulus E ′ is used to enhance the performance in the first half of the brake, the vicinity of the side wall surfaces 18A and 18B is easily extended in the tire radial direction.

On the other hand, in the conventional block 100 as shown in FIG. 3A, the side walls 100A, 100A,
100B is not depressed inward of the block than the tire radial direction straight line S passing through the end portions 102A and 102B of the new tread surface 102 along the tire circumferential direction. Therefore, the rubber volume near the side wall surfaces 100A and 100B of the block 100 is harder to extend in the circumferential direction than the vicinity of the wall surfaces 18A and 18B of the block 18.

Therefore, in a pneumatic tire in which the rotational speed is reduced to some extent in the latter half of the braking,
As shown in FIG. 3 (B) and FIG. 3 (B), when the compressed block 18 and the block 100 are going to separate from the road surface 22 (the tire rotation direction is the direction of the arrow R, and the block 18 and the block 100 are the same). In the conventional block 100, the side wall surface 10 at the time of compressive deformation is set.
Since the amount of elongation in the circumferential direction near 0A and B is small, the tread surface 1
02 indicates that the vicinity of the end 102D of the side wall surface 100D after the front and rear of the tire circumferential direction is immediately separated from the road surface 22. The vicinity of the end portion 20D of the wall surface 18D is still in the ground contact state (because the length of extension of the block end portion is large, so that the contact time is long).

Therefore, the block 18 of the present embodiment
In this case, the actual contact area volume is larger than that of the conventional block 100, and the performance in the latter half of the brake is improved.

In the pneumatic tire 10 of this embodiment, the braking performance can be improved without increasing the coefficient of friction with the road surface 22 by changing the area (negative ratio) of the tread surface 20 of the block 18 or the like. Such as increased resistance
It does not lower other performance. Second Embodiment A pneumatic tire according to a second embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 4, the side walls 24A and 24B of the block 24 of the present embodiment along the tire circumferential direction (the directions of arrows A and B) have the base side closer to the inside of the block than the tread surface portion 26 of the block. It is an inversely tapered surface that is inclined so that

Also in this embodiment, since the side walls 24A, 24B are recessed inside the block from the tire radial straight line S passing through the tire circumferential end portions 24A, 24B of the new tread 26, the side walls 24A, 24B of the tread 26 are recessed. The vicinity of 24B is easy to expand in the circumferential direction, the actual contact area volume in the latter half of the brake can be increased, and the performance in the latter half of the brake can be improved.

The inclination angle θ of the side wall surfaces 24A, 24B with respect to the tire radial straight line S is preferably set to 5 to 35 degrees.

In the above embodiment, both side surfaces in the tire circumferential direction are recessed from the straight line S in the tire radial direction, but the effect of the present invention can be obtained with only one side surface. (Test Example) In order to confirm the effect of the present invention, a conventional pneumatic tire in which a block of a conventional shape is formed in a tread, and an example pneumatic tire in which a block to which the present invention is applied is formed in a tread. Prepared, performed the actual vehicle brake test and measured the rolling resistance.

The details of the test tire will be described below. Example tire: Block shape: See FIG. 2 Block height (H): 7 mm Block new tire tread circumferential dimension (L):・ ・ Dimension of tire width direction of new tread surface of 20mm block (W) ・ ・ ・ Radius of curvature of tire circumferential side wall surface of 30mm block (R) ・ ・ ・ ・ 3mm Height of curvature center (C) of curved surface (h) 3.5mm Negative ratio 26% Dynamic elastic modulus E '・ 1.25 × 10 ⁸ dyn / cm ² Tensile stress at 300% elongation M ₃₀₀・ ・ ・ ・ ・ ・ ・ 100kgf / cm ² Conventional tire: block shape ・ ・ ・ See Fig. 3 Block height (H) ・·········· Tire circumferential dimension of new tread of 7mm block (L) ・ ・ ・ Tire width of new tread of 20mm block Direction dimension (W): 30 mm Tilt circumferential side wall inclination angle (θ): 10 degrees Negative ratio: 26% Dynamic modulus of elasticity E ': 0.90 × 10 ⁸ dyn / cm ² Tensile stress at 300% elongation M _300: 85 kgf / cm ² Next test method Will be described. -Actual vehicle brake test: The actual vehicle brake test was performed on both dry roads and wet road surfaces.

In the dry road actual vehicle brake test, the test tire was mounted on an actual vehicle, the vehicle entered the braking start position at 80 km / h, and the distance until the speed reached 0 km / h was measured.

In a wet road surface actual vehicle brake test, a test tire was mounted on an actual vehicle, the vehicle entered a braking start position at 80 km / h, and a distance until the speed became 0 km / h was measured.

The test conditions are as follows. Tire Size: 155 / 65R13 73S rim size: 13 × 4.00b pressure: front 2.0 kgf / cm ^2, the rear wheel 2.0 kgf / cm ² vehicles: DAIHATSU Co. Mira load: 1 persons boarding-rolling test rolling The resistance test was measured by a conventional rolling resistance tester.

The test results were obtained by calculating the reciprocal of the rolling resistance of each tire, and calculating the reciprocal of the rolling resistance of the conventional tire by 10
The exponent was set to 0. The higher the value, the lower the rolling resistance.

The test results are as shown in Table 1 below.

[0062]

[Table 1]

As a result of the test, the pneumatic tire of the embodiment to which the present invention is applied has improved braking performance on both the dry road surface and the wet road surface as compared with the conventional pneumatic tire.

In the pneumatic tire of the embodiment, the rolling resistance is reduced by using a rubber having a high dynamic elastic modulus E '.

The improvement in the brake performance of the pneumatic tire of the embodiment is because the performance in the first half of the brake is improved by using rubber having a high dynamic elastic modulus E ', and the performance in the second half of the brake is improved by optimizing the block shape. Because he did.

[0066]

As described above, since the pneumatic tire of the present invention has the above-described structure, it has an excellent effect that the braking performance can be improved without increasing the rolling resistance.

[Brief description of the drawings]

FIG. 1 (A) is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention, and FIG. 1 (B) is a tire meridian sectional view of the tread.

FIG. 2A is a side view of a block in a free state according to the first embodiment viewed from a tire circumferential direction, and FIG. 2B is a side view of a block which is about to be separated from a road surface viewed from a tire width direction. FIG.

FIG. 3A is a side view of a block in a free state of a conventional example viewed from the tire circumferential direction, and FIG. 3B is a side view of a block that is about to be separated from a road surface viewed from the tire width direction.

FIG. 4 is a side view of a block of a pneumatic tire according to a second embodiment as viewed from a tire circumferential direction.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 12 Tread 18 Block 18A Side wall surface 18B Side wall surface S Straight line in tire radial direction

Claims (6)

[Claims] 1. A pneumatic tire having a block pattern on a tread, wherein at least one of a side wall surface of a block along a tire circumferential direction among the side wall surfaces of the block is located inside a block in a tire radial direction straight line set at a block end. A pneumatic tire characterized by being recessed in one direction. 2. The pneumatic tire according to claim 1, wherein the side wall surface is a reverse tapered surface whose base side is inclined inward of the block from the tread side of the block. 3. An inclination angle of said side wall surface with respect to a tire radial direction is set to 5 to 35 degrees.
A pneumatic tire according to claim 1. 4. The pneumatic tire according to claim 1, wherein the side wall surface is an arcuate curved surface. 5. The pneumatic tire according to claim 4, wherein the radius of curvature of the arc-shaped curved surface is 2/3 to 3 times the block height. 6. The rubber constituting the block has a dynamic elastic modulus E ′ of 0.60 × 10 ⁸ dyn / cm ² <E ′ <1.50 ×
10 ⁸ a dyn / cm ^2, to any one of claims 1 to 5 at 300% elongation tensile stress M ₃₀₀ is characterized in that it is a _{^{60kgf / cm 2 <M 300 <}} 150kgf / cm 2 The pneumatic tire as described.